Hydraulic adjusting means for rolling mills



Feb. 18, 1969 K. J. NEUMANN 3,427,339

7 HYDRAULIC ADJUSTING MEANS FOR ROLLING MILLS rch 16, 1964 Original Filed Ma Sheet v ARL JSEF IVEl/MA/VN I ATTORNEY Feb. 18, 1969 K. J. NEUMANN 3, 2

HYDRAULIOADJUSTING MEANS FOR ROLLING MILLS Originl Filed March 16, 1964 Sheet 2 of 2 k4 RL JoseF "El/M411 A Tramway United States Patent Office 3,427,839 Patented Feb. 18, 1969 Germany, assignor ABSTRACT OF THE DISCLOSURE The invention relates to metal working and more particularly to a rolling mill frame with chocks for the rolls which are mounted adjustably in the windows of solid, unitary cast or assembled stand elements which are placed under tension by tension bolts. The chocks of a roll bear against the cross-yokes of the stands over a first pressure piston which is subjected to a variable hydraulic pressure in a first pressing chamber. By varying the pressure in the adjusting circuit established for these first pressure chambers the interval between the rolls and the rolling mill frame is altered.

This application is a continuation of my copending application Ser. No. 352,722, filed Mar. 16, 1964, now abandoned.

It is an object of the invention to provide a rolling mill frame including a hydraulic adjustment device having stand columns or tension bolts which may be placed hydraulically under a pulling pretension before the rolling operation in order to regulate during the rolling action the rolling gap. This is done by varying the elongation of the stand columns or tension bolts. This principle is well known and the invention is concerned with a particularly advantageous and simple embodiment of an arrangement for pretensioning the roll-ing mill frame.

Aside fromthe hydraulic adjusting arrangement acting directly on the checks of a roll and the first pressure chambers, the invention is characterized by a second hydraulic pressure piston with a second pressure chamber whose pressure acts over a transverse beam on a pair of pressure plates which extend on both sides of the guide surfaces of the chocks. These place the stand columns under a pulling pretension, wherein the pressure acting on the second pressure piston is independently adjustable by the pressure which is variable for adjusting the chocks in front of the first pressure piston for regulating the roll gap.

The extent of the possible adjusting distances or rolling gap variations in pretensioned rolling mill frames having a hydraulic control arrangement depends largely on the amount of stress the tension elements of the rolling mill frame are able to support. This is because they are already pretensioned before the rolling pressure is produced, in order to release a mechanical tensioning force which is stored in them and which counteracts the rolling pressure and maintains the rolling gap constant. As the requirements of the control circuit become greater it is also necessary to pretension the tensioning elements to a greater extent. For example, it may be desirable in cold rolling frames to regulate not only the variation in the thickness of the sheets, but also the reduction from one pass to the next (although it is relatively small). This may be done through an adjustment of the nominal valve by means of a hydraulic control device in order to be able to dispense with heavy adjusting motors of an auxiliary mechanical adjusting arrangement. It is therefore possible to exceed permissible stresses in the tensioning elements slightly unless one accepts a greater length of the tensioning elements and thus a greater height of the frame.

The invention provides a hydraulic adjusting arrangement for the reduction from one pass to the next which works independently of the pretension control arrangement so that the stress of the stand columns or tension bolts of the frame which is permissible from a strength aspect need comprise only the adjustment variations during the rolling operation.

In order to accommodate the first and second pressure chambers of the adjusting circuit and control circuit in a single cylinder in each instance which is set into a crossyoke of the rolling stands, it is proposed further according to the invention that the first pressure piston consist of a pressure bolt and a pot-like tensioning element. The pressure bolt bears on the floor of this tension element and its flange-like enlarged ring piston forms with a cylinder pot the first pressure chamber for the unregulated adjustment of a chock. The second pressure chamber of the hydraulic control circuit is formed by the second pressure piston which works on the transverse beam and which is guided in the same cylinder pot and by a ring piston of the pressure bolt of the first pressure piston which passes through the transverse beam.

It is true that the rolling pressure in the two circuit arrangements of the invention passes over a hydraulic pressure cushion, namely the first pressure chamber for the adjusting movement from pass to pass. However, it has been found that, as the adjusting pressure for the pass reduction is effective between the support end of the tensioning element formed into a flange-like ring piston and the cross-yoke of the stand, there is produced in view of the counteraction of the control-adjustment pressure in the first pressure chamber for the adjustment movements during the rolling operation a pressure equal to the sum of the rolling pressure and the hydraulic tensioning force. As this sum is maintained constant by the control arrangement, the provision of a hydraulic pressure cushion in the force-flow of the rolling pressure is applicable in this case.

The objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings which illus trate an embodiment of the invention, in which:

FIGURE 1 shows a stand of a rolling mill frame with a combined hydraulic control and adjusting device set into the lower cross-yoke, the adjustment and control being shown diagrammatically.

FIGURE 2 shows the control and adjustment device according to FIGURE 1 in longitudinal section and on a larger scale, and

FIGURE 3 shows a section along line 33 of FIG URE 1.

A four-high rolling mill frame according to FIGURE 1 comprises frames or stands 1 and a plurality of chocks 2 and 3. The upper chocks 2 having upper rolls 2a are adjusted by means of screw spindles 4 which are driven in a novel manner by drive motors which have just sufficient power to adjust the upper chocks when the frame is not under stress. The screw spindles 4 have only the purpose of providing a rough or coarse adjustment of the rolls or for withdrawing the rolls. The rolling pressure is produced by the combined hydraulic control adjustment devices which are set into lower cross-yokes 1a of the stands.

With reference to a single stand the lower chock 3 having a lower roll 3a rests on a pressure bolt 12 which is supported at its free end on the floor of a pot-like tension element 13 (FIG. 2). A collar 13a of the tension member is formed as an annular or ring piston with a pressure surface 13b and guided in a cylinder 14 which is set into a recess of the cross-yoke 1a. The rolling pressure which is transferred through the pressure bolt 12 is thus transmitted over the tension element 13, the pressure medium in the pressure chambers 30, and the cylinder 14 into the stand. The pressure in the pressure chamber is the variable adjustment pressure for adjusting the lower roll against the rolling pressure.

The pressure bolt 12 of the first piston unit 12, 13 has a ring piston 19 which slides also in the cylinder 14 and forms together with the cover like ring piston 20 the second pressure chamber 10. This ring piston 20 acts over a transverse beam 70 independently of the pressure bolt 12 on two plates 71, 72 which extend on both sides of the guide surfaces of the chocks 2, 3 and which bear with their ends against shoulders 1b of side frames or stand columns 10 and 1d. It is thus seen that the stand columns, without requiring that the rolls be moved against each other, may be pretensioned in order to use the resulting pretension force of the stands during the controlled rolling for making the rolling gap corrections. The pressure piston 12 passes also through the transverse beam 70.

The pressure plates 71, 72 may cover the full width of the stand columns and may carry the wear plates 73, 74 for the chocks 2 and 3. They can thus be subjected to a considerable pressure force as the danger of an outward bending is possible only inwardly where the checks which are mounted with as little play as possible to prevent an inward bending of the pressure plates.

If the admissable pressure tension at the pressure plates 72, 71 permits this, they may also be embedded in grooves of the stands which are closed as much as possible by the wear plates 73, 74 and guided so as to be safe against bending as is shown in cross-section according to FIGURE 3. The control effect is also not lost by the fact that one limits the length of the grooves and plates to a portion of the stand length. The control must operate inthat case with an over compensation in order to register the amount of rolling gap variations which are due to the stand tension in the non-pretensioned upper area.

It lies within the scope of the known control principle to apply as measuring values for the control arrangement not the pressure but the tension of the intermediate members to be influenced by the control pressure, namely of the tension element 13 and the pressure bolt 12. For this purpose the invention provides that a measuring rod 32 is introduced into a longitudinal bore of the pressure bolt 12 (FIGURE 2). The rod 'has one end facing the next chock 3 and is connected to the pressure bolt part pressing against the chock, by for example, being screwed into it. Its other free end 32a, which passes through the floor of the pot-like tension member 13 actuates a measuring device 33 for determining the displacement of the chock 3.

A differential transformer is used appropriately as the measuring device and the end 32a of the measuring rod which is screwed into the pressure bolt 12 at 3211 forms the slideable iron core. When the measuring device 33 is connected for example over two support arms 34 to the cross-yoke 1a it registers the algebraic sum of the elongations of the intermediate elements 12 and 13. It also includes any displacement of these parts as a whole when leakage losses arise in the pressure chambers 10 or 30. Also, variations of the viscosity of the pressure medium due to temperature changes have no effect because they release a signal in the measuring device 33 to which the control responds.

As may be seen from FIGURE 2 the conduits 35 for the adjusting pressure and conduits 36 for the control pressure extend laterally from the cylinder 14. Therefore, the groove in the cross-yoke 1a for receiving the cylinder 14 has groove-like recesses 37 and 38.

To explain the operation of the combined adjusting and control arrangement according to FIGURE 2 reference is made to FIGURE 1. The adjusting pressure which is introduced over conduit 35 is produced in a pump 40 which brings in the pressure medium from a storage container 41 and when valve 42 is closed, conveys it over the conduit 43 to a relief valve 44. By opening the valve 42 a predetermined pressure is produced in conduit 35 and in the pressure chamber 30. Over an adjustable relief valve 45 the adjusting pressure may be increased. A manometer 46 indicates the pressure existing in the pressure chamber 30.

From conduit 35 a conduit 47 leads also to the storage vessel 41 and a safety valve 48 is mounted in this conduit. This valve is so set that it opens as soon as an excessively high pressure develops in pressure chamber 30, for example when a double strip comes between the rollers or where no provision has been made to reduce the rolling speed upon the approach of a welding seam. In that respect the hydraulic adjusting circuit is protected by the safety valve 48 in order to prevent damage to the rolling mill frame.

The control system for the gap adjusting pressure is illustrated only diagrammatically and it may also be designed in a different manner from that shown, for example it may include a pressure converter. This control must be so designed that in pressure chamber 30 a high variable pressure may be produced, the pressure being indicated. Also, the control circuit is protected against high pressure points.

From the pressure chamber 10 for regulating the rolling gap during the rolling operation a conduit 36 leads to a control valve 50 in which a control piston 51 is mounted slideably. By opening suitable control slots depending on the direction of movement of the piston, the conduit 36 is connected either through a supply conduit 52 with the pressure source or with the discharge conduit 53. In the actual control arrangement 54, an electromagnetic setting member for moving the control piston 51, a feedback device and a device for comparing the nominal and the actual tension values are contained. The nominal control value is set at the nominal value adjuster 55 and is fed into the control device 54. The actual value is fed from the gauge 33 over conduit 56 into a comparison device 57 and passes further over conduit 58 into the control device 54. An adjusting device 59 is associated with the comparison device 57 through which a measured value from gauge 33 may be so compensated that at the indicator 60 the dial hand may be set at zero.

From the pressure conduit 36 for the pressure control a branch line 61 leads to a measuring transformer and comparison device 62 in which the hydraulic pressure is converted into an electrical value which is fed over loop 64 into the control device 54 but not into the nominalactual value comparator, but to the electromagnetic adjusting member for the control piston. By means of the adjusting device 63 the measured value of the hydraulic control pressure in the pressure chamber 10 may be compensated by comparison in such a way that the output signal for conduit 64 is zero.

Through a double switch 65 either the actual value is fed from comparison device 57 into the nominal-actual value comparator of the control device 54, or the measured value of the hydraulic control pressure is fed from the comparator 62 into adjusting member of this control device. It is thus possible to set the control arrangement to a constant rolling gap and to employ the arrangement to maintain the pressure in pressure chamber 10 constant, and this necessity will become clear from the method hereafter described for adjusting the rolling gap from pass to pass by means of the hydraulic gap adjusting device.

In cold rolling mills it is customary to run the rolls upon each other before introducing the strip, until the required rolling pressure is set, taking into consideration the pass reduction. The rolling mill is allowed to operate without load in order to obtain rolling conditions which are as realistic as possible. Thereafter the dial is set to the desired nominal value of the strip. The actual rolling gap is then smaller by the amount of the roll change, and

if the rolling pressure has been correctly set, the strip will have its desired thickness.

In order to employ the above described process of pretensioning the [frame before the rolling operations for measuring and adjusting purposes by running the rolls on each other also in the present combined hydraulic con trol and adjusting arrangement, in which the control and adjusting pressures operate against each other, the specific method is carried out as follows:

First the switch 65 is actuated in order to disconnect the rolling gap control and to switch the control to a constant control pressure in pressure chamber 10. For this purpose the adjusting device '53 is actuated until the gauge 66 indicated the desired hydraulic control pressure or the corresponding hydraulic tension force P (hydraulic pressure). In pressure chamber 30 for the gap adjusting or gap closing action any desired pressure may be present. By means of the adjusting screws 4 a coarse adjustment is given to the upper roller whereby the maxi mum stroke of the pressure bolt 12 must be taken into consideration.

Thereafter valve 42 is opened while valve 45 is closed, and the pressure in pressure chamber 30 is increased whereby the intermediate members 12 and 13 are moved together upwardly toward the lower chock. As the pressure in conduit 36 is thereby increased, a signal travels from the measuring transformer and comparator 62 over conduit 64 so as to adjust the control piston 51 to the right so that pressure medium is discharged through conduit 53 and the pressure P in pressure chamber remains constant. This is also true when the rollers roll against each other and the adjusting or biasing pressure in chamber 30 increases whereby the tension members 13 at the pressure bolt 12 are increasingly elongated or compressed.

The pressure increase in pressure chamber 30 may be read from gauge 46 but as here the sum of the rolling pressure and of the hydraulic tension force is indicated, gauge 67 is provided to show the proportion of the rolling pressure which is to be adjusted. Gauge 67 operates in dependence of a tension which is formed in the measuring transformer and comparator 68 by a comparison between the sum value of the adjusting pressure introduced through conduit 69 on the one hand and the control pressure from conduit 36 on the other hand is differential value. This difference is the rolling pressure P During the comparison of the pressures in device 68 the ratio of the effective pressure surfaces 13b and 19a (FIGURE 2) is nonvariably set. The pressure surface 19a of the control position 19 is made suitably larger than the surface 13b of the adjusting piston 13a in order to obtain also at low control pressures a suflicient hydraulic tensioning force for a control range which is as large as possible.

After the probable rolling pressure for the subsequent pass has been set, the measured value introduced from conduit 56 and which represents, practically the rolling gap zero in a pretensioned frame, the dial hand is set at the gauge 60 to Zero through the adjusting device 59. When thereafter the relief and control valve 45 is opened, the adjusting or biasing pressure decreases with a constant control pressure P and with pressure medium flowing through line 36 until valve 45 is closed, if at the gauge 60 the desired pass reduction of for example 2 mm. is indicated. As this process is accompanied by a relief action of the upper half of the frame which is not pretensioned by the pressure plates 71, 72, and also of a relief of the intermediate members 12 and 13, a rolling gap of less than 2 mm. is produced. The frame and the intermediate members have moved back the amount of this difference and as far as this elastic return or springing back of the frame is concerned, the gauge 33 does not register it, and is not intended to register it as it only records the position of the lower roller relative to the lower cross-yoke 1a of the frame.

Before the start of the rolling operation it is necessary to set the desired or nominal control value at adjuster 55. As the adjustment is made with reference to the interval of the lower chock 3 from the cross-yoke la, which existed under the artifically produced rolling forces with the rolls in contact with each other, the nominal control value had to be set previously to the indicated value on the gauge before it was set to zero.

At the start of the actual rolling operation at total pressure P +P is built up in the pressure chamber 30 of the gap adjusting or biasing control when valve 45 is closed, and this pressure was present when the rolls were operated against each other. As in gauge 33 the original measured value is also obtained according to which the nominal control value was set at adjuster 55, it is possible to return at the moment of starting the rolling operation the switch by control means, which are not shown, into the position illustrated and the connection for the rolling gap control is thus made.

-In the case of tandem or wide strip trains all the frames are set in the above discribed manner to the proper rolling gap before introducing a strip. For reverse operating cold rolling frames this is appropriate only for the first pass of the strip. Before the reversing operation the succeeding pass is adjusted as follows:

The switch 56 is switched over, so as to go from the rolling gap control to a constant control pressure control. The adjustment of the pass reduction is actuated in that the valve 42 is opened and that by means of valve 45 the pressure in pressure chamber 30 is increased by throttling or pressure control to the point where on gauge 60 whose dial was previously set to zero the desire-d pass reduction is adjusted. After this the valves 42 and 45 are closed again. The new nominal control valve is adjusted in adjuster 55 to the full measured value in gauge 33 whereby the adjuster 59 is again set to zero so that the measured value in comparator 57 is not compensated by an oppositely connected value, but is indicated fully. In this case the switch 65 may. be changed already to control before the number of revolutions of the rolls is raised, because the frame does not receive again any pressure relief. Slowly arising increases of the rolling pressure upon starting, which are caused by the lubricant or lubricant wedges, and which influence the control in the sense of a further rolling pressure increase that is giving a false rising signal, are taken into consideration by a correction of the nominal control value on the basis of a thickness measurement of the rolled material for a monitoring operation.

The advantages of the combined hydraulic gap adjusting and control arrangement according to the invention may be summed up as follows: The motors for a mechanical adjusting device and the adjusting device itself may be small and considerably less expensive because alternating current motors are employed. The adjusting movements against the rolling pressure are carried out hydraulically much more rapidly. By a counter-action of the control and of the adjusting or biasing pressure the compressibility of the pressure medium for the gap adjustment does not have any effect, although it is within the power course of the rolling pressure, if the control pressure, or the hydraulic tensioning force for the tension member 13 and the pressure bolt 12 resulting therefrom, is larger than the rolling pressure so that the full rolling pressure is adjusted upon starting the rolling operation. The presetting of the rolling pressure by operating the rolls on each other is essential in order to register the proportion of the rolling change which will pertain to the pressure fluid in pressure chamber 30 for the gap adjustment, and also to the non-hydraulically pre-tensioned frame height. The disclosed measuring arrangement registers the position of the lower chock 3 relative to the frame and receives in that respect all leakage losses which arise at the pressure chamber 10 and 30, so that it leads to a very accurate adjustment of the nominal value of the strip, as the Zero positioning from pass to pass, or in the case of rolls which have been operated in contact with each other, may be adjusted.

What is claimed is:

1. A rolling mill comprising a frame, an upper chock slideably mounted in said frame, an upper roller rotatably mounted in said upper chock, means for moving said upper chock vertically to adjust the position of said upper roller, a lower chock slideably mounted in said frame, a lower roller, rotatably mounted in said lower chock, said frame having an opening below said lower chock, said opening having a recessed portion providing a cylinder with an inner shoulder at its lower end, sleeve means disposed in said opening and having the upper end slideably received in said cylinder and closed at the lower end, said sleeve means having an outwardly directed annular flange at its upper end engaging said cylinder to provide a first fluid pressure chamber between the lower surface of said annular flange and the upper surface of said inner shoulder on said cylinder, a pressure bolt disposed in said sleeve means and engaging the closed lower end thereof and the lower side of said lower chock, said pressure bolt having an enlarged intermediate portion providing a piston having an annular upper pressure surface, annular piston means disposed in said cylinder in slideable engagement around said pressure bolt and defining a second fluid pressure chamber between the lower pressure surface thereof and said upper face of said bolt piston, means for selectively supplying a fluid biasing pressure to said first pressure chamber for tensioning said sleeve to produce movement of said chock for adjusting the rolling gap between said upper and said lower rollers, and means for maintaining a fluid control pressure in said second fluid chamber to balance said fluid biasing pressure for controlling the adjustment of the gap.

2. A rolling mill comprising a frame, an upper chock slideably mounted in said frame, an upper roller rotatably mounted in said upper chock, means for moving said upper chock vertically to adjust the position of said upper roller, a lower chock slideably mounted in said frame, a lower when rotatably mounted in said lower chock, said frame having an opening below said lower chock, said opening having a recessed portion with an inner shoulder at its lower end, a cylinder mounted in said recessed portion and having an inwardly directed flange at the lower end engaging said inner shoulder, sleeve means disposed in said opening and having the upper end slideably received in said cylinder and closed at the lower end, said sleeve means having an outwardly directed annular flange at its upper end engaging said cylinder to provide a first fluid pressure chamber between the lower surface of said annular flange and the upper surface of said inner shoulder on said cylinder, a pressure bolt disposed in said sleeve means and engaging the closed lower end thereof and the lower side of said lower chock, said pressure bolt having an enlarged intermediate portion providing a piston having an annular upper pressure surface, annular piston means disposed in said cylinder in slideable engagement around said pressure bolt and defining a second fluid pressure chamber between the lower pressure surface thereof and said upper face of said bolt piston, means for selectively supplying a fluid biasing pressure to said first pressure chamber for tensioning said sleeve to produce movement of said chock for adjusting the rolling gap between said upper and said lower rollers, means for maintaining a constant fluid control pressure in said second fluid chamber to balance said fluid biasing pressure for controlling the adjustment of the gap, and gap measuring means for varying the pressure in said fluid pressure control means in response to changes between the nominal and the actual gap values.

3. A rolling mill according to claim 2 wherein said fluid pressure control means include means for measuring the pressure in said second fluid pressure chamber to adjust said fluid in said second pressure chamber to a constant value during changes in the gap between successive passes.

4. A rolling mill according to claim 2 wherein said means for maintaining a constant fluid control pressure in said second fluid pressure chamber include a fluid pressure control valve, a pressure regulator for actuating said fluid pressure control valve, and switching means for connecting said constant fluid pressure control means and said gap measuring means to said pressure regulator.

5. A rolling mill according to claim 4 wherein said switching means is connected from said gap measuring means to said constant fluid pressure control means during adjustment of said fluid biasing pressure.

6. A rolling mill according to claim 4 wherein said gap measuring means include a gauge rod disposed in a longitudinal bore of said pressure bolt for contacting the lower face of said lower chock and fixed to said bolt at the end adjacent said chock, said rod passing through said tension member at the other end and being connected to a measuring device at said other end for actuating said gap measuring device to register the displacement of said lower chock.

7. A rolling mill according to claim 6 wherein said gap measuring device is mounted on a support fixed to said frame adjacent said sleeve means.

8. A rolling mill according to claim 1 including vertical recesses in said frame adjacent at least part of said lower chock on opposite sides thereof and having each a shoulder at its upper end, transverse plate means disposed in said recesses at the lower end for engaging said annular piston means, and elongate pressure plate means in said recesses between said transverse plate means and said shoulders to vary the tension of said frame upon movement of said annular piston means.

9. A rolling mill according to claim 1 wherein said fluid biasing pressure means include a safety valve for discharging fluid upon reaching a predetermined excess pressure.

10. In a rolling mill of the type having a plurality of checks adjustably mounted in openings in stands comprising:

(a) a stand,

(b) first and second chock means for supporting first and second roll means,

(c) one of said chock means mounted on a first pressure piston,

(d) said first piston positioned in a first pressure chamber on a cross-yoke of said stand and exposed to a variable hydraulic pressure,

(e) a second hydraulic pressure piston positioned in a second pressure chamber,

(f) said second piston operating through a substantially transverse beam on a pair of pressure plates on the sides of said one of said chock means placing stand columns of said stand under a pretension whereby pressure bearing on said second piston may be regulated independently of the variable pressure for adjusting said one of said chock means.

11. In a rolling mill as defined in claim 10 wherein said first piston includes a pressure bolt and a pot-like tension member, said pressure bolt being supported in said pot-like tension member, a cylinder for supporting said first and second pressure chambers, said pot-like tension member having a flange forming with a portion of said cylinder of said first pressure chamber.

12. In a rolling mill as defined in claim 11 wherein said second piston, said cylinder and said substantially transverse beam form said second pressure chamber.

13. In a rolling mill as defined in claim 10 having regulation means including means for adjust-ing the pressure in said first pressure chamber whereby a constant regulation pressure is maintained in said second pressure chamber.

14. In a rolling mill as defined in claim 10 including a hydraulic adjustment circuit connected to said first pressure chamber and having a safety valve therein.

15. In a rolling mill as defined in claim 11 including means for measuring the pressure on said one of said chock means including a measuring rod positioned in a bore in said bolt, said rod having one end operationally connected to said one of said chock means and having its other end actuating a measuring device for determining the displacement of said one of said chock means.

2,056,409 10/1936 Ross 72245 10 Sendzimin et a1. 72245 Fox 72243 Metzger 72245 Neumann 72246 Brown 72245 U.S. Cl. X.R 

